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Dashaba Formation

Dashaba Fm

Period: 
Mesoproterozoic

Age Interval: 
Yuxian (Stenian) (25)


Province: 
Sichuan

Type Locality and Naming

North Sichuan (southern Qinling). The Dashaba Fm was named by Chen Jiadi in 1983. The type section is in Guihuaqiaogou of Shuibai Township, Pingwu County, Sichuan Province. The formation is the lowest formation of the Bikou Gr in this region.

Synonym: （大沙坝组）


Lithology and Thickness

The formation is composed mainly of grey garnet-bearing biotite quartz schist, sericite-quartz schist, intercalated with leptite (often interpreted as meta-volcanics) and meta-tuff, with minor actinolite-schist. It is over 113 m thick.


Lithology Pattern: 
Metavolcanics


Relationships and Distribution

Lower contact

Base is not seen.

Upper contact

It is conformably overlain by the Guihuaqiaogou Fm (late Yuxian on schematic stratigraphic section, then overlain by Yinping Fm of earliest Neoproterozoic. All of these are indicated as being in the Bikou Gr.

Regional extent

North Sichuan (southern Qinling). The formation is distributed around Mupi-Wugongkou, Pingwu County, Sichuan Province.


GeoJSON

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Fossils


Age 

Schematic stratigraphic section suggests span of early Yuxian (early Stenian).

Age Span: 

    Beginning stage: 
Stenian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
1,200.00

    Ending stage: 
Stenian

    Fraction up in the ending stage: 
0.5

    Ending date (Ma):  
1,100.00

Depositional setting


Depositional pattern:  


Additional Information

In Sichuan Province, the Bikou Group is subdivided, from bottom to top, into Dashaba Fm, Guihuaqiaogou Fm and Yinping Fm. For details on the Yinping Fm, please see the Neoproterozoic System of Stratigraphic Lexicon of China.


Compiler:  

Extracts from The Mesoproterozoic Erathem (chapter in Stratigraphic Lexicon of China, draft of 2022) by Gao Linzhi, Ding Xiaozhong, Zhang Chuanheng, Zhang Heng.